An aircraft capable of hover and/or of slow flight is typically not well-suited to long-distance, efficient cruising flight. Certain fixed-wing aircraft are capable of long-distance, efficient cruising flight, but typically require long runways for takeoff and landing. When there isn't sufficient space for a runway, these fixed-wing aircraft may not be used.
While certain known aircraft-launch and/or retrieval systems and methods have eliminated the need for a runway to launch and/or retrieve a fixed-wing aircraft, they have several drawbacks.
Certain known aircraft-launch systems and methods employ a pneumatic catapult launcher to launch a fixed-wing aircraft into free flight without using a runway. These pneumatic catapult launchers include a launch carriage that runs along a track. Before launch, an operator angles the track relative to the ground to obtain a desired launch trajectory and mounts the fixed-wing aircraft to the launch carriage. The pneumatic catapult launcher accelerates and then decelerates the launch carriage along the track to eject the fixed-wing aircraft from the launch carriage, thereby launching the fixed-wing aircraft into free flight.
While these pneumatic catapult launchers are proven launch solutions that are mobile, versatile, and built for harsh environments, they have some drawbacks. These pneumatic catapult launchers can only be used in areas in which they can be positioned so the trajectory of the fixed-wing aircraft after launch clears any obstacles. For instance, they cannot be used to launch fixed-wing aircraft in heavily wooded or urban areas. These pneumatic catapult launchers are also relatively large, heavy, and cumbersome compared to the fixed-wing aircraft, which increases transportation costs and difficulty.
One known aircraft-launch and retrieval system and method, which is disclosed in U.S. Pat. No. 2,843,337 to Bennett, employs a rotary-wing aircraft to launch a fixed-wing aircraft into free flight and to retrieve the fixed-wing aircraft from free flight without using a runway. To launch the fixed-wing aircraft into free flight, the rotary-wing aircraft stiffly mates to the fixed-wing aircraft via insertion of four balls mounted atop the fixed-wing aircraft into corresponding socket structures mounted to the rotary-wing aircraft. The rotary-wing aircraft then hoists the fixed-wing aircraft, accelerates to a desired airspeed, and releases the fixed-wing aircraft into free flight. To retrieve the fixed-wing aircraft from free flight, the rotary-wing aircraft matches the airspeed of the fixed-wing aircraft, stiffly mates with the fixed-wing aircraft in midair, decelerates, and carries the fixed-wing aircraft to a desired landing area.
The Bennett aircraft-launch and retrieval system and method is impractical. Regarding launch, releasing the fixed-wing aircraft into free flight requires a perfectly synchronized release of the four balls from their corresponding socket structures. An imperfectly synchronized release will impart a pitch or roll rate to the fixed-wing aircraft as the rotary-wing aircraft releases it into free flight. Releasing some but not all of the balls from their corresponding sockets could be catastrophic, possibly resulting in the destruction of either aircraft.
Regarding retrieval, mating the four balls to their corresponding socket structures in midair requires extreme precision and dramatically increases the relative position requirements of the autopilot. The rotary-wing aircraft must match the fixed-wing aircraft's airspeed, align each socket structure above its corresponding ball, and decrease its altitude such that each socket structure receives and secures its corresponding ball. Improperly performing even part of one of these steps could result in retrieval failure or worse: damage to either aircraft. Retrieval becomes even more complex in adverse weather conditions, such as rain or high winds, in which aircraft movement becomes even more imprecise and unpredictable.
One known aircraft-retrieval system and method employs a retrieval rope suspending apparatus that suspends a retrieval rope to retrieve the fixed-wing aircraft from free flight without using a runway. The retrieval rope suspending apparatus is anchored to (or due to its weight, effectively anchored to) the ground and vertically suspends the retrieval rope. The fixed-wing aircraft is flown toward the retrieval rope such that the leading edge of one of the wings of the fixed-wing aircraft contacts the retrieval rope. Afterwards, continued movement of the fixed-wing aircraft relative to the retrieval rope causes the retrieval rope to slide away from the fuselage of the fixed-wing aircraft along the leading edge of the wing toward the wingtip until a rope capture device (such as a cleat) near the wingtip captures the retrieval rope. Rope deflection combined with a damping force imposed by a damping element slows the fixed-wing aircraft, which is then lowered to the ground.
This known aircraft-retrieval system and method is robust and has proven success in a wide range of conditions (such as in gusty winds) and for fixed-wing aircraft having autopilots with imperfect tracking. This known aircraft-retrieval system and method owes its success in part to a large, sweeping crosshair forming a large capture target area. The leading edge of the fixed-wing aircraft's wing forms the horizontal axis of the crosshair, and the retrieval rope forms the vertical axis of the crosshair.
While a proven solution in certain situations, this known aircraft-retrieval system and method has certain drawbacks. Using a ground-anchored retrieval rope limits applications to those with clear space in the vicinity of the ground anchor. Global Positioning System (GPS) reception may be denied at some retrieval locations, rendering GPS-assisted retrieval impossible. Further, if low-altitude retrieval is desired, such as retrieval in a canyon or a wooded area, options for wave-off may be limited, thereby limiting the ability to abort retrieval. Also, the retrieval rope may get snagged on surrounding obstacles, which could lead to fixed-wing aircraft damage or destruction. Additionally, operators must take care to avoid structural overload on the fixed-wing aircraft since a stationary object (the ground-anchored retrieval rope) arrests its motion. Another disadvantage is that after the fixed-wing aircraft captures the retrieval rope, the fixed-wing aircraft dangles from the retrieval rope by one wingtip. Operators must exercise much care to avoid damaging the fixed-wing aircraft, as it can begin to swing like a wrecking ball as operators lower it to the ground. Further, for large fixed-wing aircraft, sophisticated ground-handling equipment would be needed to right the fixed wing aircraft as it is lowered to the ground. For covert operations, the retrieval rope suspending apparatus could reveal the location of the base of operations, defeating the purpose of the covert operation.
There is a need for new systems and methods by which fixed-wing aircraft may be launched and retrieved without using a runway that solve these problems.